Why limit technology to only key decisions? Use it for any decision where the referee has some doubt.
The technology works and is helping clean up the game. At the moment the VAR system is only considered for four areas. Football should take a lead from other sports and use it wherever possible.
As FIFA President Gianni Infantino says, the use of goalline technology and the VAR system is "cleaning up football". The elimination of blatantly wrong decisions and goals that should never have been allowed shows football is moving forward and slowly catching up with other sports that have been harnessing technology for some time. There must always be room for improvement and although a wrong decision in a penalty box is highly likely to impact on a game's direction, so too can a missed foul in the build-up to a goal several phases earlier. A referee cannot be expected to see everything that happens on the pitch so needs as much help as he can get. It seems odd that VAR cannot be used if a clear and obvious error is made in the middle of the pitch. All the more so if the team that is wronged has no opportunity to launch a protest as they can in American Football with a flag on the play. When cricket launched its Decision Review System, they allowed teams three opportunities per innings to challenge the umpires. That has since been dropped down to two and further refinements to cope with the limitations of ball-tracking technology have been made. Given that football is a fast-paced game, FIFA could consider limiting teams to one challenge per game to prevent unnecessary delays or spurious appeals to waste time or break an opponent's rhythm - something which we see in tennis, for example.
Goalline technology and VAR has been a great help to the game and has boosted its global image by eliminating blatant errors that impact major matches. By focusing on the four areas it currently does, it limits disruption and ensures the system is only used when absolutely necessary. It makes sense to strictly limit the phases of play in which VAR can be used because there is usually far more for a referee to have to police in the penalty box or in the build-up to an attack on goal, than elsewhere on the pitch. Most fans will accept a missed foul in the centre circle if they know offside goals are a thing of the past. Football was late to the technology in sport party but that does not mean it should blindly follow others down the same paths. You only have to see how many times review systems in other sports have had to be tweaked to see that the more technology a sport uses, the more problems it can cause. There were enough issues with VAR during its testing phase to suggest that football must learn to walk confidently with technology before trying to run with it.
Currently, referees can implement the VAR system to assist with the following: goals, penalty decisions, red cards and mistaken identity. Elsewhere on the pitch, they are on their own. There is currently no way a team or player can request a review if they feel an infringement has been missed or a decision is incorrect. In fact, they are penalised if they are seen to be pressuring officials to use the system. Many other sports which were quicker to adapt technology than football do not impose such limits on its use and allow teams and players to challenge the officials' decisions.
The VAR system is limited to the four areas which have most potential to define a match's direction. Opening it up to a "no holds barred" system could add further complications and slow the game down. Allowing players and coaches to challenge a referee's decision goes against the ethos of respecting the referee's decision as final and playing to the whistle. Football was late to bring in technology but does not need to try to emulate other sports, particularly those where there are more natural breaks in which technology can be used without disrupting the flow of proceedings.